The present invention relates to a brush device.
A conventional brush device for a DC motor includes a base member, supply brushes, brush holders, and elongated terminals. The supply brushes slide against a cylindrical commutator of the motor. Each brush holder is a substantially rectangular tube and retains one of the brushes. Each terminal is retained by the base member and is connected to one of the brushes with an electric wire. The brush holders are secured to a yoke of the DC motor. Each brush holder has a ceiling that extends in the radial direction of the commutator.
To assemble the brush device, each terminal is inserted into the base member from the axial direction of the commutator and is retained at a predetermined position of the base member. Then, each brush is inserted into one of the brush holders by shifting the brush from the outer portion of the brush holder to the inner portion of the brush holder in the radial direction of the commutator. The proximal end of each brush is urged toward the commutator by a spring so that the distal end of the brush is pressed against the commutator.
When the motor is rotated, the brushes slide against the commutator. Therefore, drive current from the outside is supplied to the motor, or, more specifically, to a coil wound about a core of the motor via the terminals, the electric wires, the brushes, and the commutator.
In the brush device as mentioned above, each brush is inserted into the corresponding brush holder by simply shifting the brush from the outer portion of the brush holder to the inner portion of the brush holder in the radial direction of the commutator. Therefore, the length of the electric wires needs to be set such that each electric wire permits the corresponding brush to be shifted to the outer portion of the corresponding brush holder in the radial direction of the commutator. That is, the length of the electric wires needs to be set to a length that permits assembling of the brushes to the brush holders.
When the terminals are retained in the vicinity of the inner portions of the brush holders, the electric wires become loose after the brushes are assembled. Therefore, the material cost for the part of the electric wires that become unnecessary after the assembly is wasted. Also, the electric wires might be disconnected by, for example, vibration.